Testing device for magnetizable objects



Aug. 13, 1935. w J H. c. DRAKE 2,011,441

TESTING DEVICE FOR MAGNETIZABLE OBJECTS Filed May 29, 1934 3 nnentor Harcouri C.Drake Patented Aug. 13, 1935 PATENT OFFICE TESTING DEVICE FOR MAGNETIZABLE OBJECTS Harcourt C. Drake, Hempstead, N. Y., assignor to Sperry Products, Inc. ration of New York Brooklyn, N. Y., a corpo- Application May 29, 1934, Serial No. 728,109

' 6Claims. (Cl. 175-183) This invention relates to a method of and means for detecting internal defects such as fissures within magnetizable objects. More particularly, my invention is adapted for the detection of internal fissures in rails in track. For this purpose I propose to utilize the magnetic method of testing which consists in sending magnetic flux continuously through the rail and detecting by means of an auxiliary solenoid any variations in magnetic flux caused by the presence of internal fissures.

The difficulty with the magnetic method of testing has heretofore been that variations in magnetic fiux are caused by other factors besides internal fissures. Thus, for example, hardspots, points of stress, and differences in chemical composition are some of the factors which cause deflection of the magnetic flux to an extent substantially equal to the deflection caused by internal fissures. It was therefore impossible to distinguish between rail defects which it was desired to detect and what may be termed false defects, which in reality were not such defects as would interfere with the utility of the rail or other magnetizable object.

It is the principal object of my invention, therefore, to provide a novel method of and means for detecting fissures by the magnetic method and distinguishing between actual fissures and other unimportant defects such as hard spots, etc. The principles underlying my invention will become apparent in the following detailed descriptionof the invention.

In the accompanying drawing,

Fig. 1 is .a view largely diagrammatic illustrating the principle and mechanism comprising my invention.

Fig. 2 is an end view of the Fig. 1 device.

While I have shown my invention as applied to the testing of rails, it will be understood that it can be applied to any other magnetizable object. The magnetic method of testing isclearly illustrated in Fig. 1 wherein the rail ill to be tested is magnetized continuously by means of an electromagnet ll supplied with current from any suitable source l2, to set up flux axially of the rail. Such flux will be uniform in direction and there :ill be little or no leakage of flux outside of the rail, except in the region of a fiaw where the flux will be distorted to cause a greater leakage of lines of magnetic fiux outside the rail and such leakage may be detected by a solenoid I3 having a coil Hi. The said solenoid 13 may be mounted to maintain a constant distance above the rail. For this purpose it may be mounted, as shown, on

the energizing magnet II and said magnet ll may be in turn mounted upon a carriage I5 adapted to ride upon the rails as by means of wheels I 6. The said carriage l5 may in turn be supported upon a car I! by means such as loosely fitting 5 bolts l8 and springs l9 whereby the carriage l5 may have a movement of its own independent of the car body movement so as to maintain the energizing magnet II and the detecting magnet l3 always in constant relation to the rail head. 10 The variations in magnetic fiux caused by the presence of a flaw will cause a change in the flux through the core extending through coil l4 and will thus induce an E. M. F. in said coil which after being suitably amplified by amplifier A may be caused to operate a pen P on a travelling chart 0. Said pen P will normallytrace a straight line longitudinally of the chart but when a flaw occurs the pen will be attracted by magnet operated from the output of amplifier 20 A to cause a jog to be made in the straight line,

. which will indicate the presence of a flaw.

As stated in the introduction, the magnetic flux is distorted not only by the presence of internal fissures but by such factors as hard spots, points of stress, differences in chemical composition, etc. which are not in reality defects affecting the utility of the rail [0 and therefore it is not desired that these factors shall be detected. Heretofore,

all of these factors affected the indicator quite as much-as a fissure and it was impossible to tell from the record which of the indications were caused by fissures and which by the other factors. I have discovered, however, that if the rail is subjected to vibration near the point where 5 an internal fissure is located, such fissure will not be detected by the detector magnet I4. The

reason for this is that the faces of a fissure which are normally separated are in contact during vibration and therefore there is no displace- 4 ment of flux. Such vibration, however, does not affect the detection of the extraneous factors such as hard spots, etc. I therefore discovered a method by which I could differentiate between fissures and other extraneous factors when utilizing the magnetic method of testing.

To accomplish this purpose, I provided a second carriage l 5' supporting an energizing magnet H and detector magnet I3 with detector coil It, said carriage l5 being mounted either to the front or to the .rear of the first magnet. In the drawing, as shown, the auxiliary energizing detector magnet system is mounted ahead of the conventional detector system. Energizing mag- 3 net H is supplied with current from a suitable Y etsource such as l2 to send magnetic flux through the rail in a manner similar to that of magnet I I. Immediately adjacent detector coil [4, I mount a hammer which may be any suitable type such as a pneumatic hammer, the reciprocating member 31 of which is adapted to strike the rail immediately adjacent the detector coil I4. As a result of this construction, detector coil l4 will not pick up transverse fissures but will detect all other defects such as hard spots, etc., whereas detector coil it will detect the transverse fissures as well as hard spots, etc. nected to an amplifier A, the output of which operates a pen P by means of magnet 20', said pen 1? being displaced longitudinally of chart C from pen P a distance suflicient to compensate for the distance that coil IQ is positioned in advance of coil it. By this construction, a defect picked up by said coils in succession will appear in line upon the chart. Thus, for instance, the chart shows two indications {iii and 40' opposite one another on Chart The operator immediately understands that these indications do not indicate a transverse fissure because detector coil M does not pick up transverse fissures. Therefore, the indications it and Hi must indicate a hard spot, point of stress, etc. Indication i 8, however, made by the pen P has no counterpart on the record made by the pen P. The operator therefore knows that this indication ti indicates a transverse fissure because only the coil i i picked it up and not the coil it. By this comparative method of indication the magnetic method of testing becomes practical for the purpose of detecting transverse fissures because it provides a method whereby indications caused by such fie-=- sures may be distinguished from indications caused by other extraneous factors such as hard spots, etc., which do not affect the utility of the rail and which it is not desired to detect.

In accordance with the provisions of the patent statutes, I have herein described the principle and operation of my invention, together with the apparatus which 1 now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is-designed to use the various features and elements in the-combination and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use.

The coil I4 is con-.

Having described my invention, what I claim and desire-to secure by Letters Patent is:

l. A. device for testing magnetizable objects which comprises means for energizing said object with flux, means responsive to variations in said flux, asecond means for energizing said object with flux, a second means responsive to variations in said last-named flux, and means adjacent one of said responsive means for vibrating said object.

2; A device for testing rails in track comprising a car adapted to travel on the rails, a plurality of carriages mounted on said car in comparative relation to the rails and arranged in tandem, each carriage comprising means for energizing the rail with flux and means responsive 'to variations in said flux, and a hammer mounted on said car and adapted to vibrate the rail adjacent one of said responsive means. i

3. A device for testing rails in track comprising a car adapted to travel on the rails, a plurality of carriages mounted on said car in comparative relation to the rails and arranged in tandem, each carriage comprising means for energizing the rail with flux and means responsive to variations in said flux, a hammer mounted on said car and adapted to vibrate the rail adjacent one of said responsive means, and a plurality of indicating means adapted to be actuated by the respective responsive means arranged in comparative relation.

i. A method for detecting fissures in magnet zable objects which consists in energizing the object with flux a plurality of times, detecting varia-- tions in said flux during each energization, and vibrating the object in the region of detection during one of said energizations.

' 5. A method for detecting fissures in magnetizable objects which consists in energizing the object with flux,- detecting variations in said flux, energizing the object a second time with flux, detecting variations in said last-named flux, and vibrating the object in the region of detection during one of said energizations.

6. A method for detecting fissures in magnetizable objects which consists in energizing the object with flux, detecting variations in said flux, energizing the object a second time with flux, detecting variations in said last-named flux, vibrating the object in the region of detection during one of said energizations, and comparing said variations.

HARCO'URT C. DRAKE. 

